我们知道，在ASP.NET MVC中实现多选Select的话，使用Html.ListBoxFor或Html.ListBox方法就可以。在实际应用中，到底该如何设计View Model， 控制器如何接收多选Select的选中项呢？

 

实现效果如下：

初始状态某些选项被选中。

 

当按着ctrl键，进行重新选择多项，点击"提交"按钮，把选中项的id拼接。

 

对于Select中的项，包含显示值，Value值，以及是否选中，抽象成如下的类。

 

public class City

{

public int Id { get; set; }

public string Name { get; set; }

public bool IsSelected { get; set; }

}

 

对于整个多选Select来说，在ASP.NET MVC中，所有的选项被看作SelectListItem类型，选中的项是一个string类型的集合。于是多选Select的View Model设计为：

 

public class CityVm

{

public IEnumerable
    
       Cities { get; set; }
    

public IEnumerable
    
      SelectedCities { get; set; }
    

}

 

在HomeController中，把SelectListItem的集合赋值给CityVm的Cities属性。

 

public class HomeController : Controller

{

public ActionResult Index()

{

var cities = new List
    

{

new City(){Id = 1, Name = "青岛", IsSelected = true},

new City(){Id = 2, Name = "胶南", IsSelected = false},

new City(){Id = 3, Name = "即墨", IsSelected = true},

new City(){Id = 4, Name = "黄岛", IsSelected = false},

new City(){Id = 5, Name = "济南", IsSelected = false}

};

var citiesToPass = from c in cities

select new SelectListItem() {Text = c.Name, Value = c.Id.ToString(),Selected = c.IsSelected};

CityVm cityVm = new CityVm();

cityVm.Cities = citiesToPass;

ViewData["cc"] = citiesToPass.Count();

return View(cityVm);

}

......

}

 

在Home/Index.cshtml中,是一个CityVm的强类型视图，对于选中的项会以IEnumerable<string>集合传递给控制器。

 

@model MvcApplication1.Models.CityVm

@{

ViewBag.Title = "Index";

Layout = "~/Views/Shared/_Layout.cshtml";

}

Index

@using (Html.BeginForm("GetCities", "Home", FormMethod.Post, new {id = "myForm"}))

{

@Html.ListBoxFor(c => c.SelectedCities, Model.Cities, new {size = ViewData["cc"]})

}

 

在HomeController中，再把从视图传递过来的IEnumerable<string>拼接并呈现。

 

public class HomeController : Controller

{

......

[HttpPost]

public ActionResult GetCities(IEnumerable
    
      selectedCities)
    

{

if (selectedCities == null)

{

return Content("没有选中任何选项");

}

else

{

StringBuilder sb = new StringBuilder();

sb.Append("选中项的Id是：" + string.Join(",", selectedCities));

return Content(sb.ToString());

}

}

}